In man, gross sex differences exist in age-related changes of vascular tissue leading to focal atherogenesis. One possible explanation for these differences is a hormonal effect on the tensile properties of elastin and collagen, the structural proteins that contribute the major support to vascular tissue at high pressure loading. These studies are directed toward identifying an action of sex hormones on the quantitative and qualitative properties of vascular elastin and collagen. An "androgen-imprint" on vascular elastin and collagen identified during the past year consists of: (1) a lowering of levels of borohydride-reducible elastin and collagen cross-links; (2) an increase in the concentrations of non-reducible elastin cross-links; (3) a rise in collagen content; and (4) an increase in the static tensile properties at high pressure loading. Presently we are finding the first elements of the "androgen-imprint" in the neonatal male rat and these elements become more distinctive by 45 and 60 days of development. BIBLIOGRAPHIC REFERENCES: Sapolsky, A.I., H.D. Keiser, D.S. Howell and J.F. Woessner, Jr., Multiple forms of neutral metalloprotease activity from human cartilage. Arthritis Rheumatism 20:134, 1977. Nagase, H. and J.F. Woessner, Jr., Neutral protease from bovine nasal cartilage that digests proteoglycan. Arthritis Rheumatism 20:129, 1977.